Pressure-supply device for an electrohydraulic valve control of gas-exchange valves in internal combustion engines

ABSTRACT

A pressure-supply device for an electrohydraulic valve control of gas-exchange valves in internal combustion engines which has a fluid reservoir, a fluid output for the connection of the valve control, and a high-pressure pump which removes fluid from the fluid reservoir and delivers it under high pressure to the fluid output. To attain high pump efficiency and high system dynamics, the high-pressure pump is constructed as constant-displacement pump having a pump inlet and a pump outlet, and the pump outlet is connectible by a switchover valve alternately to the fluid output and, accompanied by blocking of the fluid output, to the fluid reservoir.

FIELD OF THE INVENTION

[0001] The present invention relates to a pressure-supply device for anelectrohydraulic valve control of gas-exchange valves in internalcombustion engines.

BACKGROUND INFORMATION

[0002] In a conventional pressure-supply device described in, forexample, German Patent Application No. DE 198 26 047, a high-pressurepump takes the form of a variable-displacement pump, regulated on thedelivery side or suction side, which supplies a variable pressure and avariable volumetric flow. The variable-displacement pump is connectedwith its pump inlet directly to the fluid reservoir, and with its pumpoutlet, is connected via a non-return valve, with a blocking directionpointing toward the pump outlet, to the pressure-supply-device fluidoutput, to which is connected a high-pressure accumulator used forstoring energy and damping pressure pulsation. The electrohydraulicvalve control is supplied with fluid under high pressure via the fluidoutput, the distributor line or rail connected to the fluid output beingdesignated as a high-pressure circuit of the electrohydraulic valvecontrol. For each valve to be controlled, the electrohydraulic valvecontrol has a hydraulic actuator or valve adjuster which has apositioning piston for the valve actuation, as well as two fluid-filledworking chambers acting on the positioning piston. All the valveadjusters are linked to the distributor line or rail, which is underhigh pressure, in a manner that, in each case, the lower workingchamber, acting in the valve-closing direction on a smaller effectivearea of the positioning piston, is connected directly to the rail, andthe upper working chamber, acting in the valve-opening direction on alarger effective area of the positioning piston, is connected to therail via a first electromagnetic control valve. In addition, the upperworking chamber of each valve adjuster is linked via a second electroniccontrol valve to a second rail forming a feedback line which leads tothe fluid reservoir.

SUMMARY

[0003] A pressure-supply device, according to an example embodiment ofthe present invention, for the electrohydraulic valve control ofgas-exchange valves may have the advantage that, by the combination of aconstant-displacement pump and a switchover valve between thehigh-pressure circuit and unpressurized circulation, the very goodefficiency of the cost-effective constant-displacement pump may beutilized, and a consumption-oriented coupling between the useful fluidflow and the circulation fluid flow is possible, so that the pressurecharacteristics in the high-pressure rail, linked to the fluid output ofthe pressure-supply device, for the electrohydraulic valve adjusters maybe directly influenced. For example, pulsations in the pressure may besmoothed by purposeful overlapping of delivery of fluid into ahigh-pressure accumulator connected to the fluid output and removal offluid from the high-pressure accumulator by the valve adjusters.Particularly when the switchover valve is designed as an electricallycontrolled solenoid valve, the switchover between delivery quantity zeroand maximum delivery is carried out extremely quickly in the millesecondrange, so that very high system dynamics are achieved. The switchovervalve may be switched synchronously with consumption, time and/or crankangle. The switchover of the constant-displacement pump to unpressurizedcirculation during delivery pause also ensures a constant cooling andlubrication of the constant-displacement pump by the fluid.

[0004] According to one advantageous example embodiment of the presentinvention, the constant-displacement pump is self-priming and isconnected with its pump inlet to the fluid reservoir. Alternatively, apresupply pump taking in fluid from the fluid reservoir may be arrangedupstream from the pump inlet of the constant-displacement pump. The oilpump of the internal combustion engine may advantageously be utilized asa presupply pump.

[0005] According to one advantageous example embodiment of the presentinvention, the switchover valve is made up of a 2/2-way solenoid valveand a non-return valve. The non-return valve is positioned in a bypasswhich connects the outlet of the constant-displacement pump to the fluidreservoir. The non-return valve, with the blocking direction pointingtoward the pump outlet, is connected on the incoming side to the pumpoutlet, at which the bypass also branches off, and is connected on theoutput side to the fluid output, and during unpressurized circulation ofthe fluid, blocks the high-pressure circuit with respect to the bypassand the high-pressure pump.

[0006] According to one alternative example embodiment of the presentinvention, the switchover valve is a 3/2-way solenoid valve, of whosethree valve connections, one valve output is connected to thepressure-supply-device fluid output making the high pressure availablefor the valve control, one valve output is connected to the fluidreservoir, and one valve input, switchable alternately to the valveoutputs, is connected to the outlet of the constant-displacement pump,so that depending upon the switching position of the solenoid valve, thehigh-pressure circuit is blocked with respect to the high-pressure pumpor is connected to it.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The present invention is described in detail in the following interms of exemplary embodiments.

[0008]FIG. 1 shows a circuit diagram of a pressure-supply device for thevalve control of gas-exchange valves of an internal combustion engine.

[0009]FIG. 2 shows an identical representation as in FIG. 1 according toa further example embodiment.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0010] The pressure-supply device shown in the block diagram in FIG. 1is used for the fluid supply of an electrohydraulic valve control ofgas-exchange valves of an internal combustion engine. Such a valvecontrol is described, for example, in German Patent Application No. DE198 26 047. For the pressure supply, the valve control is connected to afluid output 11 of the pressure-supply device via a so-called rail whichconducts fluid, preferably hydraulic oil, to all valve adjusters of thevalve control.

[0011] The pressure-supply device has a fluid reservoir 12, a presupplypump 13, a constant-displacement pump 14 and a high-pressure accumulator15 that is connected directly to fluid output 11. Fluid output 11 isconnected via a pressure-limiting valve 16, that is set to the maximumpermitted high pressure in high-pressure accumulator 15, to a returnline 17 running to fluid reservoir 12. A restrictor 18 is also arrangedin return line 17. On the intake side, presupply pump 13 is connected tofluid reservoir 12, and with its pump outlet, is connected on one handto the inlet of constant-displacement pump 14, and on the other hand, isconnected to return line 17 upstream of restrictor 18. With its pumpoutlet, constant-displacement pump 14 is connected via a switchovervalve 19 to high-pressure accumulator 15 and fluid output 11,respectively. In the example embodiment in FIG. 1, the switchover valveis designed as a 3/2-way solenoid valve 20 having spring resetting, thevalve being controlled by an electronic control unit 21 as a function ofthe fluid pressure prevailing at fluid output 11 and in high-pressureaccumulator 15, respectively. The fluid pressure is detected by a sensortaking the form of pressure gauge 22. 3/2-way solenoid valve 20 has avalve input 201 connected to the outlet of constant-displacement pump14, and two valve outputs 202, 203, to which valve input 201 may beswitched alternately depending on the switching position. Valve output202 is connected to fluid output 11 and high-pressure accumulator 15,and valve output 203 is connected to return line 17 on the input side ofrestrictor 18.

[0012] If 3/2-way solenoid valve 20 is in the switching position shownin FIG. 1, then high-pressure accumulator 15 is being charged, that isto say, constant-displacement pump 14 is delivering fluid intohigh-pressure accumulator 15 until the maximum pressure set bypressure-limiting valve 16 is reached in high-pressure accumulator 15and at fluid output 11. If 3/2-way solenoid valve 20 is transferred bycontrol unit 21 into its other switching position, then fluid output 11and high-pressure accumulator 15 are blocked vis-à-visconstant-displacement pump 14, and the outlet of constant-displacementpump 14 is connected to return line 17. This results in a nearlypressureless circulation of the fluid, and only as much energy is neededas is necessary for overcoming friction. The operating state in which noquantity of fluid is needed in the high-pressure branch of the valvecontrol, thus at fluid output 11, occurs constantly during normaloperation of the internal combustion engine, since constant-displacementpump 14 is designed for full-load requirement, and thus in wide areas ofthe engine operating map in which only small quantities must always beredelivered into the rail, is over-dimensioned for the consumptionoccurring here. If there is an increased need for fluid quantity, e.g.,as a result of the removal of fluid by the valve adjusters or because ofa necessary pressure increase in high-pressure accumulator 15 due to achange in the operating point of the internal combustion engine, then3/2-way solenoid valve 20 is reset via control unit 21 into itsswitching position shown in FIG. 1. Constant-displacement pump 14 nowdelivers fluid via fluid output 11 against the system pressure in valvecontrol 21 into the rail. The power consumption of constant-displacementpump 14 is then proportional to the product of the pressure and thevolumetric flow of the fluid.

[0013] The pressure-supply device shown in the circuit diagram in FIG. 2is modified only with respect to the design of switchover valve 19. Theremaining components match those in FIG. 1 and are designated by thesame reference numerals.

[0014] In the pressure-supply device according to FIG. 2, switchovervalve 19 has a 2/2-way solenoid valve 23 with spring resetting, as wellas a non-return valve 24. 2/2-way solenoid valve 23 has a valve input231 and a valve output 232 which are connected to each other or blockedfrom each other depending upon the switching position of 2/2-waysolenoid valve 23. Valve input 231 is connected to the outlet ofconstant-displacement pump 14, and valve output 232 is connected toreturn line 17, so that 2/2-way solenoid valve 23 is situated in abypass 25 circumventing fluid output 11 and high-pressure accumulator15, and alternately opens or blocks it. Non-return valve 24 ispositioned between the outlet of constant-displacement pump 14, andfluid output 11 and high-pressure accumulator 15, respectively, with aflow-through direction pointing toward fluid output 11 or high-pressureaccumulator 15.

[0015] If 2/2-way solenoid valve 23 is in its switching position shownin FIG. 2, bypass 25 is blocked and constant-displacement pump 14 isdelivering fluid into high-pressure accumulator 15. The maximum pressureavailable at fluid output 11 is in turn established by pressure-limitingvalve 16. If 2/2-way solenoid valve 23 is switched over into the otherswitching position against the restoring force of its resetting spring,then the outlet of constant-displacement pump 14 is linked via bypass 25to return line 17, and fluid is drawn in from fluid reservoir 12 in theunpressurized circulation and is delivered back again to fluid reservoir12. Non-return valve 24 ensures that the pressure in high-pressureaccumulator 15 and at fluid output 11, respectively, does not break downdue to open bypass 25.

[0016] In a modification of the pressure-supply device, instead ofrestrictor 18 arranged in return line 17, a pressure-limiting valve 26or a non-return valve 27 having a defined opening pressure is used, assymbolized in FIGS. 1 and 2 by components 26, 27 depicted next torestrictor 18. One is thereby able to ensure a constant intake pressurefor presupply pump 13, and to avoid cavitations during the deactivationof the outlet of constant-displacement pump 14 by opening switchovervalve 19.

[0017] According to a further modification of the pressure-supply devicedescribed, constant-displacement pump 14 is self-priming, and isconnected with its inlet directly to fluid reservoir 12, so that it ispossible to dispense with the presupply pump.

1-14. (canceled)
 15. A pressure-supply device for an electrohydraulicvalve control of a gas-exchange valve in an internal combustion engine,comprising: a fluid reservoir, a fluid output under high pressure forconnection of a distributor line of the valve control; a switchovervalve; and a high-pressure pump configured to deliver fluid from thefluid reservoir and to charge the fluid to high pressure, wherein thehigh-pressure pump is a constant-displacement pump having a pump inletand a pump outlet, the pump outlet being connectible alternately by theswitchover valve to the fluid output, and being connectible to the fluidreservoir accompanied by a blocking of the fluid output.
 16. Thepressure-supply device as recited in claim 15, wherein theconstant-displacement pump is self-priming, and the pump inlet isconnected to the fluid reservoir.
 17. The pressure-supply device asrecited in claim 15, a presupply pump configured to draw in fluid fromthe fluid reservoir connected to the pump inlet of theconstant-displacement pump.
 18. The pressure-supply device as recited inclaim 15, wherein the switchover valve includes a 2/2-way valvepositioned in a bypass connecting the pump outlet to the fluidreservoir, and a non-return valve that is connected on one hand to thepump outlet and on the other hand to the fluid output and has a blockingdirection pointing toward the pump outlet.
 19. The pressure-supplydevice as recited in claim 18, wherein the 2/2-way valve is a solenoidvalve having spring resetting.
 20. The pressure-supply device as recitedin claim 15, wherein the switchover valve is constructed as a 3/2-wayvalve having two valve outputs and one valve input switchablealternately to the valve outputs; and the valve input is connected tothe pump outlet of the constant-displacement pump, one of the valveoutputs being connected to the fluid output and the other of the valveoutputs is connected to the fluid reservoir.
 21. The pressure-supplydevice as recited in claim 20, wherein the 3/2-way valve is a solenoidvalve having spring resetting.
 22. The pressure-supply device as recitedin claim 19, further comprising: an electronic control unit that isconnected to a sensor detecting the pressure at the fluid output, andthat switches the solenoid valve depending upon a drop below or anexceeding of a pressure threshold, the solenoid valve being linked tothe electronic control unit.
 23. The pressure-supply device as recitedin claim 15, wherein the fluid output is connected via apressure-limiting valve to a return line running to the fluid reservoir.24. he pressure-supply device as recited in claim 23, wherein theconnection of the switchover valve to the fluid reservoir is produced onan output side of the pressure-limiting valve connected to the returnline
 25. The pressure-supply device as recited in claim 23, furthercomprising: a restrictor arranged in the return line.
 26. Thepressure-supply device as recited in claim 23, further comprising: apressure-limiting valve arranged in the return line.
 27. Thepressure-supply device as recited in claim 23, further comprising: anon-return valve having a defined opening pressure, the non-return valvebeing arranged in the return line.
 28. The pressure-supply device asrecited in claim 15, further comprising: a high-pressure accumulatorconnected to the fluid output.